Symptomatic os acromiale.

Os acromiale, the joining of the acromion to the scapular spine by fibrocartilaginous tissue rather than bone, is an anatomic variant that has been reported in approximately 8% of the population worldwide. It is more common in blacks and males than in whites and females. Although it is often an incidental finding, os acromiale has been identified as a contributor to shoulder impingement symptoms and rotator cuff tears. When nonsurgical management of a symptomatic os acromiale fails to relieve symptoms, surgical intervention is considered. Options include os acromiale excision, open reduction and internal fixation, and arthroscopic decompression. Excision usually is reserved for small to midsized fragments (preacromion) or after failed open reduction and internal fixation. Persistent deltoid dysfunction may result from excision of a large os acromiale. Open reduction and internal fixation preserves large fragments while maintaining deltoid function. Cannulated screw fixation has been shown to result in good union rates. Arthroscopic techniques have shown mixed results when used for treating impingement secondary to an unstable os acromiale. Associated rotator cuff tears may be addressed arthroscopically or through an open transacromial approach, followed by open reduction and internal fixation of the os acromiale.